Re: [boost] std::map<> - like structure for other than std::pair<>?

On 14 Apr 2015, at 13:26, David Hagood wrote:

Several times I have run into a use case where I have some object that I would like to access via something like a std::map<>, but which already contains a member that I would like to use as a key. Is there any data structure that "acts like a map", but instead of storing std::pair allows me to store an object directly, and specify what member of that object is the key value?

I can give a specific use case for this:

For those of you not familiar with the SCA, there is an object called CF::Properties. This is a CORBA sequence (think std::vector) of objects of {string name, CORBA::Any value}, used to store metadata. Ideally, I'd like to have an object that I could initialize from that sequence that would allow me to do things like this:

inline string &getKey(CF::Property &x) { return x.name; }

void foo(CF::Properties &meta) { mapLikeThingCF::Property,getKey myMap(meta); double sampleRate; myMap["SampleRate"] >> sampleRate; setHardwareSampleRate(sampleRate); }

You can store your objects in a std::set instead of a map and then provide a custom compare function that compared your objects given your key in them. E.g. struct my_compare { bool operator() (const MyObj& lhs, const MyObj& rhs) const{ return lhs.name < rhs.name; } }; std::set s;